Nanoporous alumino- and borosilicate-mediated Meinwald rearrangement of epoxides
作者:Thomas E. Davies、Simon A. Kondrat、Ewa Nowicka、Joseline L. Kean、Christopher M. Harris、Joseph M. Socci、David C. Apperley、Stuart H. Taylor、Andrew E. Graham
DOI:10.1016/j.apcata.2014.12.031
日期:2015.3
Nanoporous alumino- and borosilicate materials, produced using an evaporation-induced self-assembly approach (EISA), efficiently catalyse the Meinwald rearrangement of epoxides in dimethyl carbonate (DMC) to produce the corresponding carbonylcompounds in high yield and excellent selectivity.
A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports.Epoxidation tests on unsaturated terpenes (limonene, carveol and a-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO2 systems.The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction. (C) 2011 Elsevier B.V. All rights reserved.